The invention relates to the field of applicators for cosmetic products, typically mascara applicators, provided with a brush.
At the present time, hot stamping is applied to tube skirts mainly to implement decorations giving shiny effects similar to those given by noble metals, such as gold or silver. Until the present invention such decorations, being quite expensive to implement, were reserved for tubes containing products with a high added value, typically cosmetic products.
The problem intended to be resolved by the invention relates to decorating the flexible tube skirt when this can only be decorated after it has been shaped into a roll. This is certainly true in respect of tubes made of aluminum alloy. It is also systematically true for tubes made entirely of plastic material the skirt of which is obtained by extrusion and known as “plastic tubes”. It may also occur in respect of tubes made entirely of plastic material and known as “laminated tubes” or of laminated metal foil tubes.
Flexible so-called “laminated” plastic tubes include a head and a flexible skirt, obtained from a so-called “laminated” strip that generally includes several plastic layers. The skirt is obtained by cutting out of a cylindrical sleeve, itself obtained by rolling a planar strip. The rolling is effected such that the strip is shaped into a roll, with the edges of the strip being placed opposite each other, generally with a slight overlap, and then welded to each other. The roll so formed is cut to the required length to make the skirt then a tube head is welded to one end of the skirt.
Flexible so-called “plastic” tubes are obtained either entirely by molding (typically by injection), or, as in the case of laminates, by welding a head onto a cylindrical skirt, the cylindrical skirt having been in this case obtained by extruding a thin cylindrical section of plastic material, then cutting it to the required length.
In the case of laminated metal foil tubes or so-called “laminated” tubes, hot stamping can be applied to the strip before it is shaped into a roll with known techniques for printing on flat strips such as the one described in application FR 2,171,170 (Madag), where the strip is marked by a printing device comprising a swivel-mounted oscillating arm which compresses the moving strip while remaining supported on a roller or the one described in U.S. Pat. No. 5,368,680 (Kurz), where speeds can be obtained by passing the strip for marking and the transfer film into the gap between a marking roll and at least one support roll.
But “laminated” tubes are not in great demand for making decorations with shiny gold or silver effects, which can only be correctly printed by transfer film. Indeed, they have, because of the way they are shaped, a highly visible longitudinal weld, which spoils the aesthetic appearance of the tube. In fact, as seen, this type of decoration generally goes with products with high added value, such as cosmetic products, but not with a longitudinal weld that is regarded as unsightly. For this reason efforts are made to print such decorations on cylindrical surfaces that do not have an obvious longitudinal weld.
Heat transfer printing on non-planar objects such as the cylindrical skirts of flexible tubes has hitherto been carried out separately since the devices used cannot operate at rates that are compatible with the other devices in the manufacturing cycle. These devices comprise a planar tool that has at each cycle an alternate forward-backward motion, typically a so-called “backstep” forward motion. An alternate motion of this kind slows down production rates, with the result that even the most high-performance machines do not exceed 60 tubes per minute. Such an operation therefore means either reducing the speed of the whole production line (in this event, this does not exceed 60 tubes per minute whereas the other components of the production line can easily reach 120 tubes per minute), or doing the hot stamping on two parallel lines or using the existing devices, or again leaving the production lines for separate treatment (discontinuity of production).
None of these solutions is satisfactory, the first and third for obvious economic reasons, the second because it drives up capital costs (increased number of machines, complexity of transfer line since the tubes to be treated have to be split up then possibly brought back together after treatment), also because it drives up equipment changeover times and because, given the multiplicity of tools employed, it leads to reduced process capability: the industrial plant implementing the process has, given the multiplicity of the machines operating in parallel, a reduced capacity for making parts in the tolerance interval laid down in the specifications, which increases the scrap factor.
U.S. Pat. No. 6,531,018 describes a process for decorating the cylindrical walls of bottles in mass production. In this process, the cylindrical walls are run past a complex pressure head provided with transfer rollers rotating freely around a movable axis. This solution, which is certainly well adapted to mass production, also drives up capital costs.